There are a variety of parts-supplying apparatuses incorporating a part-holding member for provisionally holding a transferrable part, the part-holding member being movable between a part-receiving position where it receives a part and a part-delivering position where the part is coaxial with a supply rod in order that the part can be delivered to the supply rod at the part-delivering position. Any of these conventional part-supplying apparatuses is devoid of such a means for checking and confirming whether the part is correctly held or has already arrived at a predetermined position or not. As a result, If the part were improperly engaged with the supply rod or absent from the predetermined position due to Incorrect positioning of the part, any of these conventional part-supplying apparatuses cannot properly operate itself.
Concretely, there is such a conventional part-supplying apparatus which, subsequent to the arrival of a predetermined part at a position corresponding to axial line of a supply rod, activates movement of a supply rod in order to transfer this part to an objective position. Typically, this mechanism is described In the Japanese Laid-Open Patent Application Publication No. SHO60-131167. According to this mechanism, a predetermined part is directly forwarded to axial line of the supply rod, and then, the part is absorbed onto surface of a magnet. Then, the supply rod proceeds itself to hold the part and then carries it to an objective position. Since this conventional apparatus serially connects a step to transfer the part to the axial line of the supply rod with another step to operate the supply rod to hold the part and carry it to the objective position, actual operative time corresponds to the sum of time spent for executing both steps, thus adversely affecting operating efficiency.
The Japanese Laid-Open Patent Application Publication No. SHO58-137582 discloses such a mechanism which receives a transferrable part at a position remote from axial line and below a supply rod. After transferring the part to the axial line of the supply rod, the transferred part is lifted to the supply rod. All the component members are accommodated in a main assembly body, which include a holding member having a recessed domain to accommodate an individual part therein, an opening/closing claw secured to the inlet of the holding member, a plunger solely depressing the part held in the holding member, a bell crank, a return spring which moves the plunger back and forth, and a drive cylinder which transmits drive force to the bell crank. Since this conventional part-supplying apparatus is designed in order that all the above-referred component members are fully accommodated in a single main assembly body, all the components must be stored in it with utmost precision. Therefore, critical problem is easily generated, for example, even when minimal disorder is present, deviation easily occurs. Furthermore, since the part stored in the holding member is arranged to shift itself merely in the axial direction of the supply rod, after lifting the part, the plunger is obliged to fully reverse own movement in order to return to the original position. Therefore, when transferring a long part such as a bolt, the holding member must be lowered by such an amount corresponding to the length of the bolt. This in turn generates a need to provide the bell crank with extremely large stroke when moving itself back and forth on the way of transfering the part. In consequence, it is quite difficult for this conventional system to contract overall dimensions of the apparatus and smoothly operate it.